Banzer, Peter, <p>Max Planck Institute for the Science of Light, Günther-Scharowsky-Str.1, D-91058 Erlangen, Germany</p><p>and</p><p>Institute of Optics, Information and Photonics, Friedrich-Alexander-University Erlangen-Nuremberg, Staudtstr. 7/B2, D-91058 Erlangen, Germany